MIRI involves the use of lay-flat PE pipe to distribute irrigation water across levees in contoured and precision-graded rice fields. MIRI requires laying at least one row of PE lay-flat pipe perpendicular to and over levees of the rice field in order to disperse water between the levees to flood each rice paddy. MIRI can reduce water use by 25% in some studies and has increase yields in others.
CHS is the use of a computer program to design the appropriate number and size of holes to punch in lay flat irrigation pipe. In lay flat pipe, very low pressure (less than 1 meter of pressure) is used and the pipe is very large so that negligible friction loss is experienced. A CHS plan accounts for pipe crown elevation data, flow rate, furrow spacing, and furrow row length. A computer program is used to iterate the proper hole size along the pipe so that water is distributed evenly across the field. This process is used for both furrow irrigation and MIRI. In furrow irrigation, a small hole punch device with sizes ranging from one quarter inch to one inch, with hole sizes for every 1/16″ are used to create the holes in the pipe. Typically, holes are punched in every furrow, typically every 30 to 60 inches. CHS designs can have one hole or up to 10 hole sizes with highly variable spacing across the length of the pipeline. Currently irrigators punch holes based on experience or guess, and this results in more water being applied to some furrows than is needed and reduces the irrigation efficiency. The use of CHS can reduce furrow irrigation application volumes by 20-50%.
There are two types of multiple inlet irrigation: side inlet and multiple inlet. In the multiple inlet type, the pipe is placed in the middle of the field, and a trench must be created to facilitate deploying the pipe. The trench is necessary to ensure the pipe does not roll and it stays in place. In the side inlet type, the formation of the levee creates a furrow or ditch for the pipe to lay in. In side inlet, as the term suggests, the pipe is placed at the side of the field or levee.
Traditional methods of laying PE pipe for MIRI involves large tractors, other heavy machinery, or laying the pipe by hand. However, the large tires and heavy weight of the tractors and heavy machinery can damage rice paddy levees as they travel across the field. The damage to the levees can be difficult and time-consuming to fix. Furthermore, tractors and heavy machinery generally travel much slower than ATVs and other ATUs and can therefore take a significant amount of time to travel between rice fields to lay pipe at separate locations. Laying pipe by hand can also be very time consuming and difficult due to the weight of the rolls of PE pipe.